1. Field of the Invention
The invention relates to a technique for interrupting energization of an electrical storage device irrespective of control (program control) executed by a controller.
2. Description of Related Art
There has been suggested a technique for turning off a system main relay when charging current flows through a secondary battery in order to prevent overcharging of the secondary battery. By turning off the system main relay, it is possible to interrupt connection of the secondary battery with a load, it is possible to stop charging the secondary battery, and it is possible to prevent overcharging of the secondary battery.
On/off control over the system main relay is executed by a central processing unit (CPU) included in an electronic control unit (ECU). The CPU executes not only drive control over the system main relay but also other control, and sometimes changes a program incorporated in the CPU. Here, when the program is changed, it is necessary to check whether drive control over the system main relay, in other words, control for preventing overcharging, is normally executed after the program is changed.